Mass Shifter
by BlackWolf219
Summary: A new relic gives Arcee a chance to satisfy her curiosity with Jack.


**A/N: This is the only time I'll put something like this up.**

**Mass Shifter**

Autobot Outpost Omega one was in a state of silence as the second in command of Team Prime was bored out of her processer. Due to the need for Ratchet's "scientific" expertise, she'd been left at base to care for the children. It wasn't that she minded, it was that they were taking so fragging long she assumed they'd been ambushed by the 'Cons. She was certain they would be able handle themselves but she couldn't help but worry. Arcee needed something to take her mind off this.

Like that, she thought about the human placed under her care: Jackson Darby, the apparent equivalent to Orion Pax, the data clerk who would become Optimus Prime. Of course, he vehemently deny such things but everyone at base knew it to be true. The only thing holding Jack back from being the next Prime was his own self-doubt and species. Still, she wouldn't have him any other way (except for in a berth). That's right, she'd been having such thoughts about him recently. Of course, she knew they would only remain that way.

Still, it wasn't like it'd hurt him to have such an experience, and why not with someone he was comfortable with. Their relationship was possibly more intimate than any couple she'd seen in Jasper, and Miko was out of the question due to her tactfulness (or lack thereof.) Sure, there were plenty of mechs at base, but none of them were suitable for satisfying the itch she was feeling. Sure she had experience, but they were always with someone she cared about. Unlike a certain spider-bot being held in a stasis pod in the back, she imagined.

Smokescreen was far too insufferable to even consider. Wheeljack, she was still angry with over the situation with Miko and the Insecticons and was far too arrogant like the new recruit. Bumblebee was too childish at times and was more of a little brother. Bulkhead would be too clumsy. And Ratchet was just… Ratchet.

Sure, she'd thought about Optimus but his spark belonged to her commander somewhere out among the stars, Elita-One. Besides, there was something about Jack that drew her, excited her a little. She watched the object of her thoughts interact with Miko and Raf on the couch as they played their games. She never understood those little games they played with each other. She watched as Jack smiled at Raf's victory while Miko pouted.

Arcee smirked; it was no surprise Raf was adept at games that required speed since Bumblebee was his guardian. Immediately the base was filled with the baritone of Opitmus Prime, "Arcee we have the artifact, activate the ground bridge." The five mechs stepped through, Ratchet carrying a small device that could go around the waist.

The medic answered their unasked questions, "The mass shifter. A device capable of changing our size to better fit in with the natives of any world. It was created for the use of Decepticon Pretenders in order for infiltration but luckily its completion was halted by an Autobot attack. It can only change the user to a smaller size, say about the height of Jack or Miko, and back."

"That sounds interesting," Smokescreen reached for the device, only for Ratchet to slap his hand away.

"This is not toy! It is a dangerous device that could cause true harm in the wrong hands," the medic scolded the recruit.

"For now," Optimus announced. "We will place under safeguard until a proper use or disposal can be determined." They all nodded in agreement, the cobalt blue femme eyeing the device with intrigue. It was like Primus himself was giving her the go ahead to satisfy her curiosity with her partner. She smiled inwardly and decided to feign a need for recharge. As it was the weekend, the children were permitted to stay at base overnight.

Miko and Bulkhead wasted no time in switching the television to a monster truck rally, Smokescreen watching as well. Ratchet simply turned down his audio receptors to better focus on his work. Raf and Bumblebee went to his quarters to watch some actions movies. Optimus retreated to his quarters to do whatever Primes prefer to partying. That left her and Jack as Ratchet charged her with seeing the Mass Shifter to storage.

"I've got to work anyway," he sighed. "See ya later, Arcee." She smiled as he stepped through ground bridge. She then took the device to storage so she could think about how she could best implement it later.

**Mass Shifter**

After a long day at K/O Burger (they were all long days), Jack finally punched out and left his paper hat in the bin. Yet another "riveting" day of dealing with mostly jerks while occasionally running into a genuinely nice person. Of course, he'd had yet another run in with both Vince and Sierra, the former harassing him while the latter seemed nervous around him. She had been ever since seeing Arcee drive up, her Sadie hologram projected. No doubt, she thought Jack was spoken for.

He wouldn't lie when he said he'd had some less than noble dreams about Arcee every now and then but he never thought too much into them. He had no problem admitting Arcee was attractive in her own special way. In fact, she was more beautiful than most women on the planet but she was still different. He wouldn't get into the details about why something between them wouldn't work since it was glaringly obvious. He resigned himself to the fact that Sierra would only believe he was interested in her if she knew the truth.

He left K/O Burger and ran into the alley and phoned for a ground bridge to base. The swirling vortex appeared and Jack, making sure no one was watching, entered and found himself at base in no time. Ratchet was at the monitor and mumbled a greeting, the others apparently in their own quarters. He looked at the medic, "Where is everyone?"

"Smokescreen has joined with Wheeljack in scouting an energon mine and entered radio silence," he explained. "Bulkhead and Miko went out for some 'midnight dunebashing', Arcee is in her quarters no doubt awaiting your arrival, and Optimus is sorting through the files to give his report to Agent Fowler. Now I have to inform your mother of your arrival, so if you'll excuse me…"

Jack nodded and headed for her quarters, suddenly feeling very tired after the day's events. The base was far more intricate than its initial appearance might suggest. Most of Team Prime kept themselves close, Ratchet and Smokescreen the closest to the command center and to Optimus' quarters. Bulkhead and Bumblebee shared side by side quarters along with Miko and Raf. To ease his mother's concerns regarding his friendship with Arcee, Jack had been given his own quarters, which he suspected belonged to Cliffjumper.

He felt extremely guilty for taking away something he felt no right to, Arcee had assured him it was alright. Over time, he started to believe her words and so did she. He recently discovered a passageway that led to Arcee's own quarters, giving Jack insight to just how close she'd been to him. Arcee never spoke about it and he respected her privacy. He entered the quarters and readied himself for some sleep as the door slid back closed.

"Long day, partner," Arcee called from the passageway connecting their two rooms. She was smiling somewhat mysteriously at him but he was too tired to notice.

"I won't bore you with the details," he replied. "How about you? Anything happen while I was under the hat?"

"Nothing worth mentioning," she replied. "I've been waiting for you to get back. We need to talk about something." Jack tilted his head, his exhaustion giving way to curiosity. She gestured him towards the large berth, and he complied by climbing on with her help, blushing slightly when he felt her slender fingers run across his back. He sat crossed-legged while she sat at the edge of the berth.

"What's wrong?"

"Nothing serious," she assured. "It's just that I've noticed you've been very uncomfortable around me some days. Whenever we made eye contact, you'd blush and look away like you'd done something wrong." She watched as his cheeks tinted pink at the memories. "Why did you do that?"

"Those were..." he stammered. "Awkward days." She hilted her head as he decided to be honest. "The previous night, I had some rather… uncomfortable dreams about you. That's why it was so awkward to look at you the next day."

It didn't take long for things to click into place, "I see." That was all she needed to hear to solidify her determination when she pressed the activation device. A bright light forced Jack to shield his eyes away as he came face to face with an unbelievable sight.

**Mass Shifter**

**(Warning: Mature content ahead)**

Arcee stood before him, human sized. Her form remained unchanged as she walked across he berth toward her stunned partner. She couldn't help but smirk at his shock as he realization crossed his face. "Why are you using the mass shifter?"

"Sating curiosity," she shrugged as the lights dimmed, having determined it was time for the occupants of the base to enter recharge. Her optics glowed in the darkness, smirking at Jack as he was overcome with nervousness. Before he realized it, Arcee was straddling him, her faceplate inches from his face. Jack gulped nervously as she leaned forward, leaning back instinctively. The back of his head touched the soft fabric covering the berth.

Arcee's face hovered over his, brushing her metal lips against his organic ones. A low whimper escaped Jack as he felt her body against his, wondering if this was all some dream. He tried to keep his voice calm, "What are you doing?"

"Sating curiosity," she closed the small distance, her lips firmly pressing against his. They seemed to fit perfectly together as she moved against his mouth. Jack whimpered, closing his eyes to think straight as he felt his lips move in unison with hers. The metal of her lips was as pliable as the real thing. Arcee brought his hands to her waist.

She was aware that Jack need air to breath, so she separated earning a whimper of disappointment from him. They remained in close proximity as the human breathed heavily, staring into the femme's optics. Her servo slid down to his waistline, prompting him to catch it in the act. She couldn't help but smirk at the challenge as she continued forward, their gaze never leaving each other. He gasped as she gripped him, his length slightly aroused already.

"Nervous?" she teased.

Jack frowned, "Yeah, well, you've got more experience with this than I do." He hissed in pain as she gripped him tighter, optics narrowing.

"That supposed to mean something?"

"I mean do you really expect me to believe you've never done something like this before," he asked through the discomfort. "I didn't mean to sound like _that_ but from what Ratchet explained to us, humans and Cybertronians have similar 'mating rituals'." Her grip loosened but remained firm. "So why me, anyway?"

"You could use the experience if you ever hope to have a chance with Sierra," she reasoned, keeping her face neutral as he raised a brow at her.

"That's all, huh?"

"Should there be anything else?"

"I'm not that kind of guy."

"That's not the message I'm getting," she stroked him slightly to prove her point. "I do care about you, Jack. I think your first time would be easier with someone you know well rather than someone like Sierra, whose doesn't realize the kind of person you are."

Jack processed the information with what brain power he could muster up through Arcee's ministrations. He knew her better than any girl in Jasper, of course his shyness was to blame for that. With Arcee, he never felt like a dork or a loser; they were partners. Still, this was quiet a large step in their relationship. He was still unsure, but Arcee was stubborn and wouldn't give up, so he might as well see where this led.

"You're sure you want to do this?" he asked. She smiled at his consideration of her feelings as she leaned over and started kissing his neck. He leaned back and enjoyed the feeling as she continued to stroke him. With Cybertronians, interfacing was very simple; a mech thrusting into a femme's port with his spike. But humans were far more intimate creatures.

That's probably why Jack was so uncertain about this, due to Arcee's wanting to keep her emotions in check. Still, she wanted to ease her curiosity about him. Since her armor was basically her skin, she decided to let him keep his clothes on. She continued kissing along his neck, stopping at his jugular to give a some extra attention. A groan escaped his throat at the feeling.

Their gaze met once more as she slid down his body, stopping at his waist. She removed her servo so she could unzip his pants and pulled his length. He was big for his age, even if he wouldn't admit it. She kept her optics on him as she licked the his entire length with her glossa. The smooth metal felt like nothing he'd ever felt before and couldn't hold back a throaty moan.

She ran her glossa up and down his length before stopping at the tip, her lips wrapping around it. She sucked it gently before taking him in her mouth entirely. He groaned as he watched her, his entire length in her mouth. Her glossa gently massaged him as she gazed him, optics smirking through the darkness. She slowly drew back, the smooth metal running along him like a snake.

He almost lost it there but, through his own will, kept control as she stopped at the tip and engulfed him again. She began bobbing her helm up and down, humming gently with each movement. Jack's breathing got heavier as he savored the pleasure. He knew he wouldn't last much longer, so he sat up and grasped her helm. As much as his subconscious protested, he pulled her off him and brought to eye-level with him.

He was exposed to the cold air, her saliva having made his member slick. She smiled as he regarded her with a stern look. He leaned into her neck, gently biting the cables, earning a gasp from her. He'd helped her with damages enough times to know where she was most sensitive. He gently bit the cables as she wrapped her arms around him, pulling him closer.

"Like that?" he whispered as he continued. The femme hummed in approval as he began to tug on the wires gently. He slid his hands between her plating and played with the wiring, earning a moan from the femme. "I guess it's a good thing I help you clean up after a mission, huh?" She let out a sound akin to a growl as he continued.

He gently laid her back on the berth and moved down to between her legs. A panel slipped open and exposed her port, its design resembling a female's own nether regions, not that Jack would know. He started by sticking a finger inside, feeling the warmth of the pliable material. She gasped in air she didn't need as he started to move his finger slowly in and out. She moaned in approval as Jack became bolder and added a second finger.

"Ugh," she moaned as she enjoyed the feeling. Cybertronians may have been more advanced but humans definitely had them beat when it came to stimulating pleasure. Jack increased is speed as he thrust his fingers in her port, a blue fluid leaking out of out. She let out a growl as he removed his fingers only to moan loudly as he began licking the region. The fluid tasted sweet as opposed to the energon he expected to taste.

He kissed, licked, and sucked on her port, her servos on the back of his head pushing him forward. He stuck his tongue deeper into her as more of her fluid flowed. The taste was unbearable as he got as much as he could. He felt her insides convulse around him and splash his face with her fluid. He was painfully hard as he realized he'd just made Arcee climax.

He moved away from her port, licking up the fluids around his lips as he hovered over her, gazing into her optics. She wrapped her arms around his neck and legs around his waist, his tip brushing against her. It had been some time since she'd been penetrated so this would be just difficult as if it were her first time. Jack gulped as they stared at each other. Arcee smiled and urged him on with a simple nod.

He lowered himself into her, groaning as he entered slowly, wanting to savor as much of the experience as possible. Arcee felt her optics roll in the back of her helm as pushed his way through. Finally, his base touched hers as they gazed at each other. Jack breathed heavily as waited for her to adjust, a nod being all the confirmation needed. He pulled back slowly until his tip was all that remained, pushing back in with the same speed.

Arcee moaned with each agonizingly slow movement, Jack groaning in pleasure as he began to pick up speed. He pushed into her gently but forcefully, each thrust becoming faster and faster. She began to meet him, thrusting her hips against his. Thanks to the mass shifter, she didn't have to worry about hurting his pelvis with her metal body. Her grip on him tightened as she snaked her limbs around him.

Neither said anything, their shared gaze never wavering with each thrust as Jack rolled them over. Arcee adjusted herself and rolled her hips around him, enjoying the feeling of being able to ride him for a change. She gasped with each thrust he made into her, her voice box being strained with the pleasure she felt. She gazed down at Jack, his face contorted in pleasure but his strong blue eyes never leaving her optics. The intensity behind them sent shivers through her.

Jack sat up and wrapped his arms around her, pulling her close as they continued to thrust into each other. They buried their faces into each other's necks as Jack thrust harder into her. He gently pulled her off of him and turned over on stomach, thrusting into her from behind. He bent over her and wrapped his arms around her, her dorsal wings flattening in response. He pressed his cheek to her metal one.

Her moans were like music to him as he thrust into her with greater speed. His voice came out a harsh whisper of pleasure, "Arcee, can you get pregnant for my… fluids?"

"N-No," she managed through her own moans.

"Good," was his reply as he thrust harder into her. It didn't take long for him to make her climax again. He stiffened as his fluids filled her port. Arcee groaned in pleasure as they collapsed on the berth, somehow finding a way under the covers. Jack kicked of his shoes and socks as he started to pull out of her.

"S-St-Stay inside," she whimpered, not wanting the feeling to end.

"I don't want to go limp," he blushed.

"My body will stimulate you so you'll be ready in the morning," she said as they both entered sleep.

**Mass Shifter**

As Jack opened his eyes, he found that Arcee wasn't kidding as his member was still hard. He couldn't shake the feeling of eyes on them and heard the flash of a camera. He noticed a pair of stone faced optics staring at him through the door. Ratchet simply sighed, "Don't get up. She'd only get upset with both of us."

"I can-"

"No need for explanations," he simply pinched the bridge of his "nose". "She's been in need of that of a while and the fact that she chose you isn't all that surprising. Maybe now, she won't be as insubordinate to Optimus and the others. Now, I'll leave you both to what will no doubt be your new morning ritual." He left the room as Jack felt Arcee began to move hips against his length.

"Morning, partner," she said with closed optics and a small smile on her face.

**Mass Shifter**

**A/N: I hope you enjoyed and I apologize to anyone who may have disliked this from me. I hope you don't lose any respect for me.**


End file.
